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[an-yuh-luh s] /ˈæn yə ləs/
noun, plural annuli
[an-yuh-lahy] /ˈæn yəˌlaɪ/ (Show IPA),
a ring; a ringlike part, band, or space.
Geometry. the space between two concentric circles on a plane.
the veil remnant on a mushroom stalk.
a growth ring, as on the cross section of a tree trunk, that can be used to estimate age.
Origin of annulus
1555-65; < Latin, variant of ānulus, equivalent to ān(us) ring + -ulus -ule Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for annulus


noun (pl) -li (-ˌlaɪ), -luses
the area between two concentric circles
a ring-shaped part, figure, or space
Word Origin
C16: from Latin, variant of ānulus ring
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Contemporary definitions for annulus

See tree ring's 21st Century Lexicon
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Word Origin and History for annulus

1560s, medical, from misspelling of Latin anulus "little ring, finger ring," a diminutive of anus (see anus).

Online Etymology Dictionary, © 2010 Douglas Harper
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annulus in Medicine

annulus an·nu·lus or an·u·lus (ān'yə-ləs)
n. pl. an·nu·lus·es or an·nu·li (-lī')
A circular or ring-shaped structure.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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annulus in Science
Plural annuluses or annuli (ān'yə-lī')
  1. A ringlike figure, part, structure, or marking, such as a growth ring on the scale of a fish.

  2. A ring or group of specialized cells around the sporangia of many ferns. By changing shape in response to variations in humidity, it breaks open the sporangium and then releases the spores with a whipping motion.

  3. The ringlike remains of a membrane (called a veil), found around the stipes of certain basidiomycete mushrooms. The presence or absence of an annulus is often used to identify the species of an individual mushroom.

  4. The figure bounded by and containing the area between two concentric circles.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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